EFFECT OF ACCLIMATION TEMPERATURE ON TEMPERATURE RESPONSES OF PORPHYRA-LEUCOSTICTA AND ENTEROMORPHA-LINZA FROM THE GULF-OF-THESSALONIKI, GREECE

The effect of the acclimation temperature on the temperature tolerance of Porphyra leucosticta, and on the temperature requirements for grow th and survival of Enteromorpha linza was determined under laboratory conditions. Thalli of P. leucosticta (blade or Conchocelis phases), ac climated to twenty-five degrees, survived up to 30 degrees C, i.e. 2 d egrees C more than those acclimated to 15 degrees C which survived up to 28 degrees C. Lower temperature tolerance of both Porphyra phases t hat were acclimated to 15 degrees C was -1 degrees C after an 8-week e xposure time at the experimental temperatures. The upper temperature t olerance of E. linza also increased by 2 degrees C, i.e. from 31 to 33 degrees C, when it was acclimated to 30 degrees C instead of 15 degre es C. The lower temperature tolerance increased from 1 to -1 degrees C , when it was acclimated to 5 degrees C instead of 15 degrees C. E. li nza thalli acclimated for 4 weeks to 5 or 10 degrees C reached their m aximum growth at 15 degrees C, i.e. at a 5 degrees C lower temperature than those acclimated to 15 or 30 degrees C. These thalli achieved hi gher growth rates in percent of maximal growth at low temperatures tha n those acclimated to 15 or 30 degrees C. Thalli acclimated for 1 week to 5 degrees C reached their maximum growth rate at 20 degrees C and achieved growth rates at low temperatures similar to those recorded fo r thalli acclimated to 15 degrees C. Thalli of E. linza acclimated for 4 weeks to 5 degrees C lost this acclimation after being post-cultiva ted for the same period at 15 degrees C. That was not the case with th alli acclimated for 8 weeks to 5 degrees C and post-acclimated for 4 w eeks to 15 degrees C. These thalli displayed similar growth patterns a t 10-25 degrees C, while a decline of growth rate was observed at 5 or 30 degrees C. The significance of the acclimation potential of E. lin za with regard to its seasonality in the Gulf of Thessaloniki, and its distribution in the N Atlantic, is also discussed.